Targeted cooling of deployable microwave antenna and methods of use

ABSTRACT

The present disclosure relates to devices and methods for the treatment of tissue with microwave energy. The devices and methods disclosed herein utilize an antenna assembly which includes an elongate member, an outer conductor, an inner conductor, at least a portion of which is deployable, and a cooling system. The cooling system disclosed herein may significantly curtail any theoretical, or potential negative effects upon the target tissue experienced during the transmission of microwave energy to the antenna assembly due to ohmic heating.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.12/277,951, filed Nov. 25, 2008, now U.S. Pat. No. 8,292,880, whichclaims the benefit of, and priority to, U.S. Provisional PatentApplication 60/990,350, filed Nov. 27, 2007, the entirety of each ofwhich is hereby incorporated by reference herein for all purposes.

BACKGROUND

1. Technical Field

The invention relates generally to microwave antennas that may be usedin therapeutic or ablative tissue treatment applications. Moreparticularly, the invention relates to devices and methods forregulating, maintaining, and/or controlling a temperature of microwaveantennas used in such applications.

2. Background of the Related Art

Many procedures and devices employing microwave technology are wellknown for their applicability in the treatment, coagulation, andtargeted ablation of tissue. During such procedures, the antenna of amicrowave probe of the monopole, dipole, or helical variety, as isconventional in the art, is typically advanced into the patient eitherlaparoscopically or percutaneously until the target tissue is reached.

Following the introduction of the microwave probe, during thetransmission of microwave energy to the target tissue, the outer surfaceof the antenna may sometimes reach unnecessarily high temperatures dueto ohmic heating. When exposed to such temperatures, the treatment site,as well as the surrounding tissue, may be unnecessarily andunintentionally effected. The present disclosure contemplates curtailingsuch tissue effects by providing improved microwave tissue treatmentdevices, cooling systems, and methods.

To prevent such unnecessarily high temperatures, several differentcooling methodologies are conventionally employed.

SUMMARY

A need exists in the art for an improved microwave tissue treatmentdevice incorporating a cooling or temperature control system thatminimizes unnecessarily high temperatures during tissue treatment.

The present disclosure is directed to a microwave tissue treatmentdevice for the therapeutic treatment or ablation of tissue. In oneembodiment, a microwave tissue treatment device is disclosed thatincludes an antenna assembly having an elongate member with proximal anddistal ends that defines a longitudinal axis, outer and inner conductorsdisposed within the elongate member that extend along the longitudinalaxis, a dielectric material interposed between the outer and innerconductors, and a sleeve at least partially disposed about a distalportion of the inner conductor and defining a cavity therearound, thecavity having a proximal end and a distal end. At least a portion of theinner conductor is deployable such that the antenna assembly maytransition from a first position to a second position. The device alsoincludes a cooling system associated with the antenna assembly thatincludes at least one inflow member and at least one outflow member,each of which is configured to circulate at least one fluid within thecavity such that at least a section of the inner conductor is in fluidcontact therewith.

The cavity defined by the sleeve may include at least two regions, suchas, for example, a proximal region, an intermediate region, and a distalregion. In one embodiment, the microwave tissue treatment deviceincludes at least one baffle member for defining at least two regions ofthe cavity. In another embodiment, the at least one baffle memberdefines at least two axial dimensions within the cavity.

In yet another embodiment, the microwave tissue treatment device coolingsystem includes first, second, and third inflow and outflow members, thefirst inflow and outflow members, the second inflow and outflow members,and the third inflow and outflow members being in fluid communicationwith a respective proximal, intermediate, and distal regions of thecavity defined by the sleeve.

The microwave tissue treatment device may include at least onetemperature sensor operatively connected to the cavity, or a regionthereof.

In another embodiment, the microwave tissue treatment device includes afirst baffle member and a second baffle member disposed within thecavity. The first baffle member and the proximal end of the cavitydefine a proximal region of the cavity of the sleeve, the first bafflemember and the second baffle member define an intermediate region of thecavity, and the second baffle member and the distal end of the cavitydefine a distal region of the cavity. The first baffle member isconfigured to substantially prevent the communication of fluid betweenthe proximal and intermediate regions, while the second baffle member isconfigured to substantially prevent the communication of fluid betweenthe intermediate region and the distal region. The first baffle memberand the proximal end of the cavity define a first axial dimension, whilethe first baffle member and the second baffle member define a secondaxial dimension, and the second baffle member and the distal end of thecavity define a third axial dimension. In one embodiment, the firstaxial dimension is greater than the second axial dimension.

In another embodiment, the proximal region of the cavity has a firstinternal diameter, and the intermediate and distal regions have secondand third internal diameters, respectively. In one embodiment, the firstinternal diameter is greater than the second internal diameter, and thesecond internal diameter is greater than the third internal diameter.

In one embodiment of the present disclosure, at least a portion of theinner conductor has a substantially arcuate profile when deployed,whereas in an alternate embodiment, at least a portion of the innerconductor has a substantially non-arcuate profile when deployed. Inanother embodiment, at least a portion of the inner conductor has asubstantially tapered profile.

The fluid may be chosen from the group consisting of water, saline,ammonium chloride, sodium nitrate, and potassium chloride, and the fluidmay be circulated with a pump.

According to another aspect of the present disclosure, an improvedmicrowave tissue treatment device is disclosed that includes an antennaassembly having an outer conductor and an inner conductor with adielectric material interposed therebetween, where at least a portion ofthe inner conductor is deployable. The device also includes a sleevethat is at least partially disposed about a distal portion of the innerconductor, thereby defining at least one cavity, at least one bafflemember disposed within the sleeve such that at least two regions of thecavity is defined, and a cooling system. The cooling system includes atleast one inflow member and at least one outflow member, each of whichis in fluid communication with the cavity defined by the sleeve.

According to a further aspect of the present disclosure, a method ofcooling a microwave antenna includes providing a cooling systemincluding at least one inflow and outflow member, each being in fluidcommunication with at least a portion of the microwave antenna, andflowing a cooling fluid through the cooling system such that the coolingfluid is in fluid communication with at least a portion of the microwaveantenna.

These and other features of the microwave tissue treatment device andmethod of use disclosed herein will become more readily apparent tothose skilled in the art from the following detailed description ofvarious embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present disclosure are described hereinbelowwith references to the drawings, wherein:

FIG. 1 is a schematic illustration of a microwave tissue treatmentsystem including a microwave tissue treatment device, in accordance withan embodiment of the present disclosure;

FIG. 2A is a transverse, cross-sectional view of a feedline of themicrowave tissue treatment device of FIG. 1, as taken through 2A-2A ofFIG. 1;

FIG. 2B is a longitudinal, cross-sectional view of the feedline of themicrowave tissue treatment device of FIG. 1, as taken through 2B-2B ofFIG. 1;

FIG. 3 is a perspective view of an antenna assembly of a microwavetissue treatment device, in accordance with an embodiment of the presentdisclosure, shown in a non-deployed condition;

FIG. 4 is a perspective view of the antenna assembly of FIG. 3, shown ina deployed, linear condition;

FIG. 5 is a perspective view of an antenna assembly of a microwavetissue treatment device, in accordance with an embodiment of the presentdisclosure, shown in a deployed, arcuate condition;

FIG. 6 is a perspective view of an antenna assembly of a microwavetissue treatment device, in accordance with another embodiment of thepresent disclosure, shown in a deployed condition;

FIG. 7 is a perspective view of an antenna assembly of a microwavetissue treatment device in accordance with another embodiment of thepresent disclosure, shown in a deployed condition;

FIG. 8 is a perspective view of an antenna assembly of a microwavetissue treatment, including a cooling system, according to oneembodiment of the present disclosure;

FIG. 8A is a perspective view of an antenna assembly of a microwavetissue treatment, including a cooling system, according to anotherembodiment of the present disclosure;

FIG. 8B is a perspective view of an antenna assembly of a microwavetissue treatment device, including a cooling system, according to stillanother embodiment of the present disclosure;

FIG. 8C is a perspective view of an antenna assembly of a microwavetissue treatment device, including a cooling system, according to yetanother embodiment of the present disclosure;

FIG. 8D is a front view of the antenna assembly of FIG. 8C;

FIG. 9 is a side, plan view of an antenna assembly of a microwave tissuetreatment device in accordance with another embodiment of the presentdisclosure;

FIG. 10 is a side, plan view of an antenna assembly of a microwavetissue treatment device in accordance with yet another embodiment of thepresent disclosure;

FIG. 11 is a perspective view of an antenna assembly of a microwavetissue treatment device in accordance with another embodiment of thepresent disclosure, shown in a deployed condition; and

FIG. 12 is a side, plan view of an antenna assembly of a microwavetissue treatment device in accordance with another embodiment of thepresent disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the drawings and in the description that follows, the term“proximal”, as is traditional, will refer to the end of the apparatusthat is closest to the clinician, while the term “distal” will refer tothe end that is furthest from the clinician.

Referring now in detail to the figures, in which like referencesnumerals identify similar or identical elements, there is illustrated,in FIG. 1, a microwave tissue treatment system 10 in accordance with thepresent disclosure. System 10 includes a microwave tissue treatmentdevice 1000 having an antenna assembly 100 connected to a power sourceor supply 20, e.g. a microwave or RF generator or any suitable powergenerating device suitable for energizing the tissue treatment device1000, through a feedline 30. Microwave tissue treatment device 1000 mayinclude a pump 40, e.g. a peristaltic pump or the like, as a mechanismfor circulating a cooling or heat dissipative fluid through device 1000,as described below. Device 1000 may further include a pusher ordeployment assembly 50 that includes a deployment knob 52, wheredeployment knob 52 is operatively engaged with or coupled to the antennaassembly 100, as described in further detail below.

Referring now to FIGS. 1-2B, as indicated above, device 1000 iselectrically connected to generator or power supply 20 by feedline 30.Feedline 30 may be any suitable conductive pathway capable oftransferring an electrical current to tissue treatment device 1000. Inone embodiment, as seen in FIGS. 2A-2B, feedline 30 may be a coaxialcable composed of an inner conductor 102, an outer conductor 104, and adielectric 106 interposed between inner and outer conductors 102, 104 toelectrically separate and/or isolate inner and outer conductors 102,104from one another. Inner and outer conductors 102, 104 may each be madeof a suitable conductive material that may be semi-rigid or flexible,while dielectric 106 may include any number of suitable non-conductivematerials such as ceramic and polytetrafluoroethylene (PTFE). Inner andouter conductors 102, 104 of feedline 30 may incorporate any suitableconductive material or metal, including, but not limited to, silver,copper and gold. In certain embodiments, inner and outer conductors 102,104 of feedline 30 may include a conductive or non-conductive substrateplated or coated with a suitable conductive material.

Feedline 30 may range in length from about 1 foot (0.3048 m) to about 15feet (4.572 m), or greater, if required in a particular application. Asdepicted in FIG. 1, feedline 30 has a proximal portion 108 operativelyconnected to, or connectable to, power supply 20 at proximal end 110,and a distal portion 112 that forms a part of microwave tissue treatmentdevice 1000, as disclosed below.

Referring now to FIGS. 1, 3 and 4, microwave tissue treatment device1000 includes an antenna assembly 100 having an elongate member 114disposed about a distal portion 112 of feedline 30, and a sleeve 116that at least partially surrounds a distal portion 102 a of the innerconductor, as described in further detail below.

Elongate member 114 has proximal and distal ends 118, 120 and defineslongitudinal axis “A”. Elongate member 114 may be formed of any materialsuitable for electrically insulating a clinician or operator from theinner and outer conductors 102, 104 of feedline 30 disposed therein suchthat the antenna assembly 100 may be handled during use.

Elongate member 114 conceals a distal portion 102 a (FIG. 3) of theinner conductor 102 when the microwave tissue treatment device 1000 isnot in use so as to prevent unintentional damage or injury, as well asthe distal portion 112 of feedline 30, which includes distal portions102 a, 104 a, and 106 a of the inner conductor, the outer conductor, andthe dielectric, respectively. Accordingly, the inner conductor, theouter conductor, and the dielectric are not only components of thefeedline 30, but also constitute components of antenna assembly 100.

At least a portion of the inner conductor, i.e. distal portion 102 a, isdeployable from distal portion 104 a of the outer conductor, such thatthe antenna assembly 100 may transition from a first, non-deployedcondition (FIG. 3), to a second, deployed condition during use (FIG. 4),as described in further detail below. In the first condition, the distalportion 102 a of the inner conductor is at least partially disposedwithin the distal portion 104 a of the outer conductor and the elongatemember 114. In the second, deployed condition, the distal portion 102 aof the inner conductor extends at least partially beyond a distal end120 of elongate member 114, such that contact may be made with thetarget tissue (not shown).

Movement from the first position to the second position may befacilitated through the use of any suitable mechanism, such as, forexample, a deployment assembly 50 (FIG. 1). Reference may be made tocommonly owned U.S. Patent Publication No. 2004/0267156, filed Apr. 4,2004, for a detailed discussion regarding the components andfunctionality of deployment assembly 50.

In one embodiment, as seen in FIG. 4, antenna assembly 100 includes adistal portion 102 a of an inner conductor that exhibits a substantiallynon-arcuate profile when deployed. In an alternate embodiment, as seenin FIG. 5, antenna assembly 200 includes an inner conductor with adistal portion 202 a that exhibits a substantially arcuate profile whendeployed. Reference may be made to commonly owned U.S. Pat. No.7,197,363 for a detailed discussion of the structure of arcuatemicrowave antenna configurations.

In another embodiment, as seen in FIG. 6, antenna assembly 300 includesa distal portion 302 a of an inner conductor that is not entirely formedof a conductive material. In this embodiment, distal portion 302 a ofthe inner conductor includes a radiating member 324 with one or moreconductive surfaces 326. Conductive surface or surfaces 326 may have aparticular pattern or distribution for focusing or dispersing the energytransmitted into distal portion 302 a of the inner conductor. Forexample, radiating member 324 may have a conductive surface 326 on onlyone side or in one particular area or region thereof.

Referring back to FIGS. 3 and 4, sleeve 116 is disposed about distalportion 102 a of the inner conductor in such a manner so as to define acavity 128. Sleeve 116 may be fixedly, releasably, or slidably connectedto distal portion 102 a in any suitable manner including, but not beinglimited to, welding or adhering, as would be appreciated by one skilledin the art. Sleeve 116 has proximal and distal ends 130, 132 defined bythe points at which sleeve 116 is connected to distal portion 102 a. Inone embodiment, as best seen in FIG. 4, the distal-most tip 134 ofdistal portion 102 a extends beyond the distal end 132 of sleeve 116. Inanother embodiment, however, as best seen in FIG. 7, antenna assembly400 may include a sleeve 416 connected to a distal portion 402 a of aninner conductor at the distal-most tip 434 thereof, or at a pointtherebeyond (not shown).

Referring again to FIGS. 3 and 4, proximal end 130 of sleeve 116 may belocated at any suitable location along the length of distal portion 102a of the inner conductor, dependent upon the desired volume of cavity128. Although depicted as substantially incisive, the present disclosurecontemplates that distal-most tip 134 may be substantially arcuate,duckbilled, or any other such configuration suitable for facilitatingthe entry of the microwave tissue treatment device into the tissue of apatient.

Sleeve 116 may be formed of any suitable biocompatible, impermeablematerial capable of retaining fluid therein, including and not limitedto PTFE and tetrafluorethylene-perfluorpropylene (FEP). The presentdisclosure contemplates that sleeve 116 may be either substantiallyrigid, or substantially non-rigid in character.

In one embodiment, as seen in FIG. 8, antenna assembly 500 includes asleeve 516 defining a cavity 528 around a distal portion 502 a of aninner conductor, and one or more baffle member(s) 542, 544 disposedwithin sleeve 516 that function to divide or compartmentalize cavity 528into individual regions 536, 538, 540. Each region 536, 538, 540 definesa respective section 546, 548, 550 of the distal portion 502 a of theinner conductor. In an alternate embodiment, as seen in FIG. 8A, theindividual regions 536, 538, 540 are not defined by physical bafflemembers 542, 544 (FIG. 8), but are rather defined constructively asvirtual baffle members 542 _(A), 544 _(A) by the interaction of acorresponding number of fluids, e.g. one fluid within each of individualregions 536, 583, 540, which may be immiscible. The incorporation of oneor more fluids into antenna assembly 500 will be discussed in furtherdetail below.

First or proximal region 536 and first section 546 of distal portion 502a have a first axial dimension L₁, and are defined by the location ofthe proximal end (not shown) of the sleeve 516 and the location of firstbaffle member 542. Second or intermediate region 538 and second section548 of distal portion 502 a have a second axial dimension L₂, and aredefined by the location of first baffle member 542 and the location ofsecond baffle member 544. And third or distal region 540 and thirdsection 550 of distal portion 502 a have a corresponding third axialdimension L₃, and are defined by the location of second baffle member544 and the location of distal end 532 of sleeve 516.

In this embodiment, first and second baffle members 542, 544,respectively, serve not only to define the metes of the three regions536, 538, 540 of cavity 528 of sleeve 516, in conjunction with theproximal end 528 (not shown) and the distal end 530 thereof, but alsoserve to substantially prevent any co-mingling of cooling fluid orfluids that may be circulated throughout each of the proximal,intermediate, and distal regions 536, 538, 540, as described below. Thepresent disclosure contemplates that cavity 528 of sleeve 516 may bedivided into any suitable number of regions dependent upon therequirements of the procedure and the application in which the microwavetissue treatment device may be employed.

With continued reference to FIG. 8, third or distal section 550 of thedistal portion 502 a of the inner conductor may comprise the area ofactive heating during tissue treatment or ablation. It may be desirable,therefore, to prevent the temperature in distal section 550 fromreaching excessively high temperatures in order to maintain optimalenergy delivery and to maintain optimal thermal therapy of the tissue.Second or intermediate section 548 of distal portion 502 a may alsobecome hot due to ohmic and conductive heating from distal section 550.Since intermediate section 548 may be in contact with the tissuesurrounding the target site, it may be desirable to allow intermediatesection 548 to achieve a particular temperature profile dependent uponthe procedure in which the antenna assembly 500 is employed.

As an illustrative example, where coagulation of the insertion tract maybe desirable, the clinician may want to allow intermediate section 548of distal portion 502 a of the inner conductor to attain a particularpredetermined temperature capable of creating a coagulating effect inthe insertion tract. In other applications, it may also be desirable,however, to prevent the temperature in intermediate section 548 fromrising beyond a particular threshold to protect surrounding sensitivetissue structures from undesired effects. During use, first or proximalsection 546 of distal portion 502 a may also come into contact with theskin of a patient. Accordingly, since proximal section 546 of distalportion 502 a may also be subject to ohmic and/or conductive heating, itmay therefore be desirable to maintain the temperature of this sectionbelow a specific temperature, particularly in percutaneous orlaparoscopic procedures, to prevent undesired effects upon the skinsurface of the patient. In other procedures, such as in applicationswhere lesions are located deep within the tissue, it may be desirable toallow the proximal section 546 to become heated to allow for thecoagulation of the insertion tract.

With continued reference to FIG. 8, antenna assembly 500 furtherincludes a cooling system 552 for regulating the temperature of distalportion 502 a of the inner conductor. The cooling system 552 operates inconjunction with, and is fluidly connected to, cavity 528 of sleeve 516such that one or more cooling or heat dissipative fluids “F” may becirculated therethrough. Fluid “F” serves to dissipate some of the heatgenerated by the antenna assembly 500 during use and may also act as amedium that modifies the dielectric constant of the distal portion ofthe antenna assembly. Potential dissipative fluids include, but are notlimited to, water, saline, liquid chlorodifluoromethane, or any suitableperfluorocarbon fluid, such as Fluorinert®, distributed commercially byMinnesota Mining and Manufacturing Company (3M™), St. Paul, Minn., USA.The fluid circulated through cooling system 552 may vary depending uponthe desired cooling rate and the desired tissue impedance matchingproperties. In various embodiments, gases, such as air, nitrous oxide,nitrogen, carbon dioxide, etc., may also be utilized as the dissipativefluid. In yet another variation, a combination of liquids and/or gasesmay be utilized.

During circulation, the heat dissipative fluid is in contact with thosesections 546, 548, 550 of distal portion 502 a of the inner conductorwithin respective regions 536, 538, 540 of cavity 528 defined by sleeve516 such that the heat generated therein may be dissipated through thefluid “F”. The cooling system 552 includes one or more inflow tubes 554,556, 558, and one or more respective outflow tubes 560, 562, 564 tocirculate the dissipative fluid “F”. Cooling system 552 may also includeat least one pump 40 (FIG. 1) in fluid communication with each inflowtube 554, 556, 558 and each outflow tube 560, 562, 564 for facilitatingthe circulation of the dissipative fluid “F”.

Cooling system 552 may include any number of inflow and outflow tubessuitable for circulating a dissipative fluid throughout the cavity 528defined by sleeve 516, anti/or any individual regions thereof. Coolingsystem 552 may also employ any number of inflow and outflow members influid communication with each section 546, 548, 550 of distal portion502 a of the inner conductor. In some embodiments, one or more regionsof cavity 528 may not be in fluid communication with cooling system 552.

As seen in FIG. 8, each of the proximal, intermediate, and distalregions 536, 538, 540, respectively, has a corresponding inflow tube554, 556, and 558 in fluid communication therewith, and a correspondingoutflow tube 560, 562, and 564 in fluid communication therewith. Inparticular, a proximal end (not shown) of first inflow tube 554 may beconnected to pump 40 (FIG. 1), while a distal end 566 of first inflowtube 554 is in fluid communication with proximal region 536, therebyallowing dissipative fluid to flow, either constantly or intermittently,into the proximal region 536 of cavity 528 defined by sleeve 516. Uponentering proximal region 536, the dissipative fluid “F” comes intodirect contact with the proximal section 546 of distal portion 502 a ofthe inner conductor, allowing for the direct convective cooling ofproximal section 546. In conjunction with first inflow tube 554, aproximal end (not shown) of first outflow tube 560 may be connected topump 40 (FIG. 1), while a distal end 572 of first outflow tube is influid communication with proximal region 536, thereby allowing thedissipative fluid “F” to flow, either constantly or intermittently, outof the proximal region 536, and return to the pump 40 (FIG. 1). In sodoing, during operation, heat generated by proximal section 546 ofdistal portion 502 a of the inner conductor, disposed within theproximal region 536 of the cavity 528 defined by sleeve 516, may beregulated and/or dissipated.

As with the proximal region 536, a dissipative fluid may be pumped intoand out of intermediate region 538 through respective distal ends 568,574 of the second inflow and outflow tubes 556, 562 thereby dissipatingthe heat generated by the intermediate section 548 of distal portion 502a of the inner conductor through the fluid circulated therein.

Likewise, a dissipative fluid may also be circulated into and out of thedistal region 540 through respective distal ends 570, 576 of the thirdinflow and outflow tubes 558, 564 thereby dissipating the heat generatedby the distal section 550 of distal portion 502 a of the inner conductorthrough the fluid circulated therein. In some embodiments, the fluid mayact as a medium that modifies the dielectric constant of the antenna.

With continuing reference to FIG. 8, inflow tubes 554, 556, 558 mayenter cavity 528 through apertures (not shown) at the proximal end ofsleeve 516 (not shown). First inflow tube 554 and first outflow tube 560are configured such that their respective distal ends 568, 580 are influid communication with proximal region 536. Second and third inflowtubes 556, 558 and second and third outflow tubes 562, 564 may continuethrough proximal region 536, through apertures 590 in first bafflemember 542, and into intermediate region 538. Second inflow tube 556 andsecond outflow tube 562 are configured such that their respective distalends 572, 584 are in fluid communication with intermediate region 538.Third inflow and outflow tubes 558, 564 continue through intermediateregion 538, through apertures 590 in second baffle member 544, and intodistal region 540. Third inflow and outflow tubes 558, 564 areconfigured such that their respective distal ends 576, 588 are in fluidcommunication with distal region 540.

In this embodiment, each of the proximal end of the cavity 528, thefirst baffle member 542, and the second baffle member 544 include sealmembers 592 associated with apertures 590. Seal members 592 may be anymember suitable to substantially prevent the escape of any fluidcontained within respective regions of cavity 528, through the apertures590, including, and not limited to a seal, gasket, or the like. Sealmembers 592 may be formed of any suitable material, including and notlimited to, a polymeric material. Seal members 592 may alsosubstantially prevent the intermingling of the cooling fluids circulatedthrough each of the proximal, intermediate, and distal regions 536, 538,540 of cavity 528.

Referring momentarily to FIG. 8B, antenna assembly 600 includes acooling system 652 having inflow tubes 654, 656, 658 and outflow tubes660, 662, 664. In this embodiment, inflow tubes 654, 656, 658 andoutflow tubes 660, 662, 664 enter cavity 628 defined by sleeve 616through apertures 690 formed therein. In this embodiment, inflow tubes654, 656, 658 may traverse elongate member 614 along its outer surface,connecting to either a common pump 40 (FIG. 1), or to individual pumps,as described above. Correspondingly, outflow tubes 660, 662, 664 mayalso traverse the outer surface of elongate member 116, connecting toeither the common pump 40 (FIG. 1) or to the individual pumps. In thisembodiment, sleeve 616 is adapted with sealing member or members 692 atapertures 690 to substantially prevent the escape of any fluid containedin cavity 628 defined by sleeve 616 through apertures 690.

In another embodiment, as seen in FIGS. 8C-8D, antenna assembly 600 mayinclude one or more channels 694 formed in the elongate member 614 thatare configured to respectively receive at least a portion of inflowtubes 654, 656, 658 and outflow tubes 660, 662, 664. Alternatively,channels 694 may be formed in outer conductor 604, dielectric material606, or in any other suitable location.

Referring again to FIG. 8, given the desirability of controlled heatingand temperature regulation within the individual sections 546, 548, and550 of distal portion 502 a of the inner conductor and the correspondingregions 536, 538, and 540 of the cavity 528, the axial locations offirst and second baffle members 542, 544 within cavity 528 may be variedas desired or necessary. By varying the location of baffle members 542and 544 in different embodiments, the axial length of the proximal,intermediate and distal regions 536, 538, and 540 may be varied. Invarying the axial length of a region, the overall volume of that regionmay be varied, and accordingly, the volume of dissipative fluidcirculated within that region may also be varied. As would beappreciated by one of ordinary skill in the art, an inverse relationshipexists between the volume of dissipative fluid within a particularregion of the cavity 528 and the temperature of that region, in that asthe volume of fluid is increased, the temperature of the region willdecrease. As an additional means of regulating temperature, the flowrate of fluid “F” into each regions 536, 538, and 540 of the cavity 528may be controlled or varied, e.g. through the use of multiple pumps (notshown).

The baffle members 542, 544 may be located at any suitable or desiredpoint within the cavity 528 defined by the sleeve 516. In oneembodiment, baffle members 542, 544 are positioned such that the first,second and third axial dimensions, L₁, L₂, and L₃, respectively, ofproximal, intermediate, and distal regions 536, 538, 540 aresubstantially equivalent. In another embodiment, baffle members 542, 544are positioned such that the first axial dimension L₁, of proximalregion 536, is greater than the second and third axial dimensions L₂ andL₃, respectively, of intermediate and distal regions 538, 540. In yetanother embodiment, baffle members 542, 544 are positioned such that thethird axial dimension L₃, of distal region 540, is greater than thefirst and second axial dimensions L₁ and L₂, respectively, of proximaland intermediate regions 536, 538. In alternate embodiments, the presentdisclosure contemplates locating the baffle members 542, 544 such thatthe overall volume of the cavity 528 may be distributed amongst anyindividual regions thereof in any suitable manner.

Referring now to FIGS. 9 and 12, in other embodiments, antenna assembly700 includes a sleeve 716 that defines a cavity 728 having proximal,intermediate, and distal regions 736, 738, and 740 defined by first andsecond baffle members 742, 744. In this embodiment, proximal,intermediate, and distal regions 736, 738, and 740 have a first, asecond, and a third radial dimension or diameter D₁, D₂, and D₃,respectively. In accordance with the present disclosure, radialdimensions D₁, D₂, and D₃ of the proximal, intermediate, and distalregions 736, 738, and 740 may be varied so as to control the volume ofeach region, and accordingly, the volume of dissipative fluid circulatedtherethrough. By varying the volume of dissipative fluid circulatedthrough each individual region 736, 738, and 740 of the cavity 728, thetemperature of each region may be substantially regulated, as discussedabove.

In one embodiment, the first, second and third radial dimensions, D₁,D₂, and D₃, respectively, are substantially equivalent. In anotherembodiment, as illustrated in FIG. 9, the first radial dimension D₁, ofproximal region 736, is greater than the radial dimensions D₂ and D₃,respectively, of intermediate and distal regions 738 and 740. In yetanother embodiment, as illustrated in FIG. 12, the third radialdimension D₃, of distal region 740, is greater than the radialdimensions D₁ and D₂, respectively, of proximal and intermediate regions736 and 738. In alternate embodiments, the present disclosurecontemplates that the radial dimensions D₁, D₂, and D₃, respectively, ofeach region 736, 738, and 740 of the cavity 728 defined by the sleeve716, may be varied in any suitable manner.

Referring now to FIG. 10, in one embodiment, the present disclosurecontemplates an antenna assembly 800 that includes a sleeve 816 defininga cavity 828 with a radial dimension D. In this embodiment, radialdimension D of cavity 828 is varied in a continuously decreasing mannerover the axial length thereof, such that a generally tapered profile isexhibited. While the antenna assembly 800 includes a sleeve 816 defininga cavity 828 that is not compartmentalized into any regions, the taperedprofile may be applicable to any of the embodiments disclosed hereinabove.

In another embodiment, seen in FIG. 11, an antenna assembly 900 isdisclosed that includes one or more temperature sensors 994 coupled to adistal portion 902 a of an inner conductor for monitoring a temperaturefluctuation at or about the distal portion 902 a. It may be desirable tomonitor the temperature of the distal portion 902 a, and/or the tissuethat may come into contact therewith, or with sleeve 916, in an effortto guard against overheating and/or the unintended therapeutic effectson the tissue. This may be particularly useful in applications wheremicrowave energy is used for treating or ablating tissue around theradiating portion. In alternate embodiments, temperature sensors 994 maybe coupled or otherwise incorporated into antenna assembly 900 at anysuitable location, including, but not being limited to sleeve 916, suchthat the temperature of the distal portion 902 a of the inner conductorand/or the cavity 928 may be monitored. In various embodiments,temperature sensor or sensors 994 may be located on the sleeve 916,e.g., on an external surface thereof, or within the sleeve 916, e.g.,within the cavity 928 which the sleeve 916 defines, using any suitablemeans, e.g. adhesives. The temperature sensor or sensors 994 may belocated on a baffle member or members 942, 944, if any. Temperaturesensors 994 may be configured for electrical connection to power source20 (FIG. 1).

The temperature sensor or sensors 994 may be a semiconductor-basedsensor, a thermister, a thermocouple or other temperature sensor thatwould be considered as suitable by one skilled in the art. Anindependent temperature monitor (not shown) may be coupled to thetemperature sensor. Alternatively, a power supply with an integratedtemperature monitoring circuit (not shown), such as one described inU.S. Pat. No. 5,954,719, may be used to modulate microwave power outputsupplied to the antenna assembly. Other physiological signals, e.g. EKG,may also be monitored by other medical instrumentation well known to oneskilled in the art and such data applied to control the microwave energydelivered to the antenna assembly.

A closed loop control mechanism, such as a feedback controller with amicroprocessor, may be implemented for controlling the delivery ofenergy, e.g., microwave energy, to the target tissue based ontemperature measured by the temperature sensor or sensors 994.

Although the illustrative embodiments of the present disclosure havebeen described herein with reference to the accompanying drawings, theabove description, disclosure, and figures should not be construed aslimiting, but merely as exemplifications of particular embodiments. Itis to be understood, therefore, that the disclosure is not limited tothose precise embodiments, and that various other changes andmodifications may be effected therein by one skilled in the art withoutdeparting from the scope or spirit of the disclosure.

What is claimed is:
 1. A microwave ablation probe, comprising: anelongated shaft defining a longitudinal axis and having proximal anddistal ends; an outer conductor disposed along the longitudinal axiswithin the elongated shaft; a dielectric material disposed coaxiallywithin the outer conductor; an antenna disposed coaxially within thedielectric material and movable between a proximal non-deployed positionwherein the antenna is substantially within the outer conductor, and adistal deployed position wherein the antenna extends distally from theouter conductor, the antenna comprising: an inner conductor disposedcoaxially within the dielectric material; and a cooling sleeve disposedcoaxially about a the distal portion of the inner conductor having acooling chamber defined therein; at least one inflow conduit in fluidcommunication with the cooling chamber and configured to deliver coolantthereto; and at least one outflow conduit in fluid communication withthe cooling chamber and configured to remove coolant therefrom.
 2. Themicrowave ablation probe according to claim 1, wherein the coolingchamber includes a baffle radially separating the cooling chamber into afirst cooling region and a second cooling region.
 3. The microwaveablation probe in accordance with claim 2, wherein the at least oneinflow conduit includes a first inflow conduit in fluid communicationwith the first cooling chamber and a second inflow conduit in fluidcommunication with the second cooling chamber; and wherein the at leastone outflow conduit includes a first outflow conduit in fluidcommunication with the first cooling chamber and a second outflowconduit in fluid communication with the second cooling chamber.
 4. Themicrowave ablation probe in accordance with claim 1, further includingat least one temperature sensor configured to sense a temperature of theantenna.
 5. The microwave ablation probe in accordance with claim 1,wherein the inner conductor is laterally biased such that, when in thedistal deployed position, the inner conductor assumes a curvate shape.6. The microwave ablation probe in accordance with claim 5, wherein inthe distal deployed position, the curvate shape of the inner conductordefines an arc of up to about ninety degrees.
 7. The microwave ablationprobe in accordance with claim 1, wherein the cooling sleeve is formedfrom a substantially rigid material.
 8. The microwave ablation probe inaccordance with claim 1, wherein the cooling sleeve is formed from asubstantially non-rigid material.
 9. A method of performing microwaveablation, comprising: providing a microwave ablation probe comprising:an elongated shaft defining a longitudinal axis and having proximal anddistal ends; an outer conductor disposed along the longitudinal axiswithin the elongated shaft; a dielectric material disposed coaxiallywithin the outer conductor; an inner conductor disposed coaxially withinthe dielectric material; an antenna disposed coaxially within theelongated shaft and movable between a proximal non-deployed positionwherein the antenna is substantially within the shaft, and a distaldeployed position wherein the antenna extends distally from the shaft,the antenna assembly having a cooling sleeve having a plurality ofcooling chambers disposed coaxially about an inner conductor configuredto deliver microwave energy to tissue; a plurality of inflow conduits,each one of the plurality of inflow conduits in fluid communication witha corresponding one of the plurality of cooling chambers; and aplurality of outflow conduits, each one of the plurality of outflowconduits in fluid communication with a corresponding one of theplurality of cooling chambers; and a plurality of temperature sensors,each one of the plurality of temperature sensors in thermalcommunication with a corresponding one of the plurality of coolingchambers; selecting a target temperature for at least one correspondingone of the plurality of cooling chambers; delivering microwave ablationenergy to tissue via the antenna; sensing a temperature of at least oneof the plurality of temperature sensors; comparing the sensedtemperature to the target temperature; and regulating the flow ofcoolant to at least one of the cooling chambers to maintain the sensedtemperature below the target temperature.
 10. A method of performingmicrowave ablation in accordance with claim 9, further comprisingextending the antenna from the proximal non-deployed position to thedistal deployed position.
 11. A method of performing microwave ablationin accordance with claim 9, wherein the coolant is selected from thegroup consisting of water, saline, liquid chlorodifluoromethane,perfluorocarbon fluid, air, nitrous oxide, nitrogen, and carbon dioxide.12. A method of performing microwave ablation in accordance with claim9, wherein the flow of coolant is regulated by varying the output of aperistaltic pump.
 13. A method of performing microwave ablation inaccordance with claim 9, further comprising regulating the delivery ofmicrowave energy to tissue to maintain the sensed temperature below thetarget temperature.
 14. A method of performing microwave ablation inaccordance with claim 9, further comprising monitoring a physiologicalsignal; and regulating the delivery of microwave energy to tissue inresponse to the physiological signal.
 15. A method of performingmicrowave ablation in accordance with claim 14, wherein thephysiological signal comprises an EKG signal.
 16. A microwave ablationprobe, comprising: an elongated shaft defining a longitudinal axis andhaving proximal and distal ends; an outer conductor disposed along thelongitudinal axis within the elongated shaft; a dielectric materialdisposed coaxially within the outer conductor; an inner conductordisposed coaxially within the dielectric material; an antenna memberdisposed coaxially within the elongate shaft and movable between aproximal non-deployed position wherein the antenna member issubstantially within the shaft, and a distal deployed position whereinthe antenna member extends distally from the shaft, the antenna assemblyincluding a cooling sleeve having a plurality of cooling chambersdisposed coaxially about an inner conductor configured to delivermicrowave energy to tissue; a plurality of inflow conduits, each one ofthe plurality of inflow conduits in fluid communication with acorresponding one of the plurality of cooling chambers; and a pluralityof outflow conduits, each one of the plurality of outflow conduits influid communication with a corresponding one of the plurality of coolingchambers; and a plurality of temperature sensors, each one of theplurality of temperature sensors associated with a corresponding one ofthe plurality of cooling chambers and configured to sense a temperaturethereof.
 17. The microwave ablation probe in accordance with claim 16,wherein the plurality of cooling chambers are separated by at least onebaffle radially positioned therebetween.
 18. The microwave ablationprobe in accordance with claim 17, wherein the baffle is configured tosubstantially prevent fluid communication between the plurality ofcooling chambers.
 19. The microwave ablation probe in accordance withclaim 16, wherein a first of the plurality of cooling chambers includesa first axial dimension and a second of the plurality of coolingchambers includes a second axial dimension that is different from thefirst axial dimension.
 20. The microwave ablation probe in accordancewith claim 16, wherein a first of the plurality of cooling chambersincludes a first radial dimension and a second of the plurality ofcooling chambers includes a second radial dimension that is differentfrom the first radial dimension.